This invention relates to an interface device for any automobile telephone which includes a data transmission device.
A conventional telephone for an automobile includes a radio transmitter/receiver and a telephone-set. The telephone-set is connected to the radio transmitter/receiver via two voice lines and two serial data lines. Usually, an interface device, which is often called a Network Control Unit, is interconnected between the radio transmitter/receiver and the telephone-set. The interface device includes a switch which selectively connects the radio transmitter/receiver to one of the telephone-sets and a data transmission device through the voice lines.
When the user wishes to transmit some data to a remote terminal, the user manually operates the dial from the telephone-set in order to connect the data transmission device to the remote terminal.
Such a conventional device is disclosed in Japanese Laid Open Patent No. HO2-57051 and No. HO3-265348.
In the conventional telephone device, however, the user has to operate the telephone-set manually before transmitting data to the remote terminal. Therefore, the user has to ring off or redial in the case of a busy or not answerable situation at the remote terminal.